The economics of modern food production have caused a migration of much of livestock raising from dispersed, free range feeding of livestock to more concentrated operations, such as feedlots, dairy cow operations, and the like. Feedlots and other concentrated livestock raising methods decrease the time and labor required to feed the animals and reduce to some extent livestock body weight lost in moving stock around to grazing areas. It allows better control of the types of food ingested and makes the mechanization of food and water rationing more practical.
One of the problems with feedlots and concentrated livestock raising is the concentration of animal waste manure products that results. The problems involve not only aesthetic concerns, but also concerns about livestock and human health and effects on wildlife, plants, and soil. Good livestock raising practice and responsible environmental impact require that livestock wastes be treated and carefully managed rather than simply dumped raw into waterways and landfills.
Waste treatment methods range from simple lagoons in which bacterial action breaks waste products into less harmful components to digesters in which bacterial breakdown is aided by mechanical means. In general, waste treatment results in a mixture of solids suspended within a water based effluent. Settling occurs by gravity, based on the density of the solids, and the solids concentration ranges from near pure water near the top of a lagoon or digester tank to a heavy concentration at the bottom.
Another concern of feedlot operators is balancing the nutritional needs of livestock to maximize body weight with the cost of feeds. With typical feed rations, as much as 80 per cent of the feed ration consumed by dairy cows, for example, passes through undigested and provides no nutritional benefit to the cows. Feed rations for cattle include various combinations of feed grains, hay, silage, and feed supplements, such as minerals, and may vary with the breed, type, age, and weight of the cattle and additionally with geographical region, season, and feed availability.